Apparatus and method for laser radiation

ABSTRACT

There is provided an improvement on homogeneity of annealing performed utilizing radiation of a laser beam on a silicon film having a large area. In a configuration wherein a linear laser beam is applied to a surface to be irradiated, optimization is carried out on the width and number of cylindrical lenses forming homogenizers  103  and  104  for controlling the distribution of radiation energy density in the longitudinal direction of the linear beam. For example, the width of the cylindrical lenses forming the homogenizers  103  and  104  is set in the range from 0.1 mm to 5 mm, and the number of the lenses is chosen such that one lens is provided for every 5 mm-15 mm along the length of the linear laser beam in the longitudinal direction thereof. This makes it possible to improve homogeneity of the radiation energy density of the linear laser in the longitudinal direction thereof.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an apparatus for annealing asemiconductor material by means of irradiation with a laser beam.

[0003] 2. Description of Related Art

[0004] Techniques for crystallizing amorphous silicon films byirradiating them with a laser beam have been known. Other techniqueshave been known wherein irradiation with a laser beam is performed torecover crystallinity of a silicon film which has been damaged as aresult of implantation of impurity ions and to activate implantedimpurity ions.

[0005] As a typical example of the latter kind of techniques, atechnique has been known wherein regions which are to become a sourceand a drain of a thin film transistor are annealed by irradiating themwith a laser beam after implanting impurity ions which are typicallyphosphorus or boron.

[0006] Such a process utilizing irradiation with a laser beam (generallyreferred to as “laser process”) is characterized in that it causessubstantially no thermal damage to a substrate. This is because a methodutilizing irradiation with a laser beam only instantaneously heat theirradiated surface and the effect of the heating is not extended to thesubstrate.

[0007] This feature of causing no thermal damage to a substrate isimportant in fabricating active matrix type liquid crystal displayswhich recently have an expanding range of application.

[0008] There are demands for use of glass substrates as substrates ofactive matrix type liquid crystal displays from the viewpoint of costand needs for such displays with a larger surface area.

[0009] However, a glass substrate can not withstand a heating process attemperatures as high as 600° C. or more or 700° C. or more. Oneeffective technique for avoiding this problem is to perform thecrystallization of a silicon film and the annealing after implantationof impurity ions as described above utilizing irradiation with a laserbeam.

[0010] According to a method utilizing irradiation with laser beams,even if a glass substrate is used, there is substantially no thermaldamage to the glass substrate. It is therefore possible to fabricate athin film transistor having a crystalline silicon film even with a glasssubstrate.

[0011] However, since the area of a laser beam is small, a laser processhas problems including low efficiency in processing a large area and lowhomogeneity in processing a large area.

SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide a techniquefor a laser process used in fabrication of semiconductor devices whereinhomogeneous annealing can be performed on a large area.

[0013] FIGS. 1(A) and 1(B) show an example of a laser radiationapparatus that employs the present invention. In FIGS. 1(A) and 1(B),101 designates a laser oscillator which oscillates a laser beam bydecomposing a predetermined gas using high frequency discharge torealize a state referred to as “excimer state”.

[0014] For example, a KrF excimer laser oscillates a laser beam by meansof high frequency discharge using Kr and F as material gases.

[0015]102 through 105 designate homogenizers. A homogenizer isconstituted by a set of cylindrical lenses. The homogenizers 102 and 105have a function of splitting a laser beam oscillated by the laseroscillator into parallel beams in a vertical direction to performoptical correction in the vertical direction.

[0016] The optical correction in the vertical direction contributes tohomogenization of the energy density of a laser beam in the direction ofthe width of a line into which the laser beam is ultimately shaped.

[0017] Further, the homogenizers 103 and 104 have a function ofsplitting a beam in a horizontal direction to perform optical correctionin the horizontal direction.

[0018] The optical correction in the horizontal direction contributes tohomogenization of the energy density of a laser beam in the longitudinaldirection of a line into which the laser beam is ultimately shaped.

[0019]106 designates a lens for controlling focusing of a laser beam inthe horizontal direction. The lens 106 contributes to focusing of alinear laser beam in the longitudinal direction thereof.

[0020]107, 108 and 110 designate a lens system for controlling focusingof a linear laser beam in the direction of the width thereof. Theprimary function of this lens system is to shape the ultimately radiatedlaser beam into a linear configuration. 109 designates a mirror. A laserbeam reflected by the mirror 109 is ultimately directed to a surface tobe irradiated 111 through the lens 110.

[0021] For example, the surface to be irradiated 111 is a surface of anamorphous silicon film or a surface of a crystalline silicon film onwhich crystallinity is to be enhanced.

[0022] What is important is the setting of optical parameters of thehomogenizers 103 and 104 for controlling the distribution of theradiation energy density of a laser beam in the horizontal direction(which corresponds to the longitudinal direction of the linear laserbeam).

[0023] In general, variation occurs in the radiation energy density inthe longitudinal direction of a linear laser beam unless the opticalparameters of the homogenizers 103 and 104 are properly set.

[0024] The present invention is characterized in that variation in theradiation energy density in the longitudinal direction of a linear laserbeam is corrected by optimizing the optical parameters of thehomogenizers 103 and 104.

[0025] A set of the homogenizers 102 and 105 is provided in a differentdirection than another set of the homogenizers 103 and 104.

[0026] FIGS. 3(A) and 3(B) show photographs of a surface of acrystalline silicon film obtained by irradiating an amorphous siliconfilm with a laser beam.

[0027]FIG. 3(A) shows the result of annealing performed by forming thehomogenizer 104 in FIGS. 1(A) and 1(B) using twelve cylindrical lenseshaving a width of 5 mm.

[0028]FIG. 3(B) shows the result of annealing performed by forming thehomogenizer 104 in FIGS. 1(A) and 1(B) using five cylindrical lenseshaving a width of 6.5 mm.

[0029]FIG. 2 is an enlarged view of the homogenizer indicated by 104 inFIGS. 1(A) and 1(B). The homogenizer 201 is constituted by a pluralityof cylindrical lenses 202.

[0030] Importantly, the number of the cylindrical lenses in thedirection of the width of a laser beam incident upon the homogenizer is7 or more, preferably 10 or more. The direction of the width of thelaser beam must coincide or substantially coincide with the longitudinaldirection of the line into which the laser beam is ultimately shaped.

[0031] Further, the width “a” of the cylindrical lenses 202 in FIG. 2must be 5 mm or less. Again, the direction of this width must coincideor substantially coincide with the longitudinal direction of the lineinto which the laser beam is ultimately shaped.

[0032] The length of the linear laser beam used for the annealing thatprovided the result as shown in FIG. 3(A) was 12 cm in its longitudinaldirection. Any change in the length of the laser beam in thelongitudinal direction still results in a difference in the effect ofannealing as shown in FIGS. 3(A) and 3(B).

[0033] Homogeneous annealing as shown in FIG. 3(A) can be achieved whenthe above-described conditions are satisfied.

[0034] If there is any deviation from the above-described conditions, avertically extending stripe pattern will be observed as shown in FIG.3(B). This stripe pattern originates from variation in the radiationenergy density of the linear laser beam in the longitudinal directionthereof.

[0035] The horizontally extending stripe pattern in the photograph(horizontal stripes) is variation caused during irradiation with alinear laser beam which is being scanned and is simply attributable toinsufficient compliance to the conditions for radiation.

[0036] The difference in the effect of annealing as indicated by FIGS.3(A) and 3(B) is attributable to improper setting of the opticalparameters of the homogenizer 104.

[0037] According to one aspect of the present invention, there isprovided an apparatus for radiating a linear laser beam characterized inthat the width of cylindrical lenses forming a homogenizer forcontrolling the distribution of energy density of the linear laser beamin the longitudinal direction thereof is in the range from 0.1 mm to 5mm.

[0038] According to another aspect of the invention, there is providedan apparatus for radiating a linear laser beam characterized in that thelength (mm) of the linear laser beam in the longitudinal directionthereof and the number of cylindrical lenses forming a homogenizer forcontrolling the distribution of energy density of the linear laser beamin the longitudinal direction thereof are in the range defined bycoordinates represented by (100, 7), (700, 50), (700, 140), and (100,20).

[0039] The above-described coordinates are shown in FIG. 7. Therelationship shown in FIG. 7 indicates that high homogeneity is achievedwhen the length of the linear laser ultimately radiated in thelongitudinal direction thereof that corresponds to one cylindrical lensis generally in the range from 5 mm to 15 mm.

[0040] According to another aspect of the present invention, there isprovided an apparatus for radiating a linear laser beam characterized inthat it comprises a homogenizer for controlling the distribution ofenergy density of the linear laser beam in the longitudinal directionthereof and in that the width (mm) of the laser beam incident upon thehomogenizer corresponding to the longitudinal direction and the width(mm) of cylindrical lenses forming the homogenizer are in the rangedefined by coordinates represented by (30, 0.1), (80, 0.1), (80, 5),(50, 5) and (30, 3).

[0041] The above-described coordinates are shown in FIG. 8. Therelationship shown in FIG. 8 satisfies a condition that the width of thelaser beam incident upon the homogenizer is in the range from 30 mm to80 mm; the laser beam is divided by the homogenizer into 10 or morebeams; and the width of the cylindrical lenses is in the range from 0.1mm to 5 mm.

[0042] The homogenizer has a configuration as indicated by 201 in FIG. 2and is constituted by a multiplicity of cylindrical lenses indicated by202.

[0043] For example, the homogenizer for controlling the distribution ofthe energy density of a linear laser beam in the longitudinal directionthereof is indicated by 103 and 104 in FIGS. 1(A) and 1(B).

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIGS. 1(A) and 1(B) schematically show an optical system of alaser radiation apparatus.

[0045]FIG. 2 is a schematic view showing a configuration of ahomogenizer.

[0046] FIGS. 3(A) and 3(B) are photographs showing a thin film.

[0047] FIGS. 4(A) through 4(F) illustrate steps of fabricating a thinfilm transistor.

[0048]FIG. 5 illustrates radiation of a linear laser beam.

[0049] FIGS. 6(A) and 6(B) schematically show an optical system of alaser radiation apparatus.

[0050]FIG. 7 illustrates the relationship between the number ofcylindrical lenses and the length of a linear laser beam in thelongitudinal direction thereof.

[0051]FIG. 8 illustrates the relationship between the width ofcylindrical lenses and the width of a laser beam incident upon ahomogenizer.

[0052]FIG. 9 shows a beam profile of a rectangular laser wave which hasbeen passed through a homogenizer split into nine parts.

[0053]FIG. 10 shows a beam profile of a rectangular laser wave which hasbeen passed through a homogenizer split into eighteen parts.

[0054]FIG. 11 illustrates the relationship between the number ofcylindrical lenses and the length of a linear laser beam in thelongitudinal direction thereof.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0055] A first embodiment of the present invention will now bedescribed.

[0056] The present embodiment relates to an optical system in which thenumber of homogenizers can be one half of that in the optical systemshown in FIGS. 1(A) and 1(B).

[0057] FIGS. 6(A) and 6(B) show the optical system of the presentembodiment. In the optical system shown in FIGS. 6(A) and 6(B), a laserbeam oscillated by an oscillator 601 is shaped by an optical systemconstituted by lenses 602 and 603 into a laser beam having apredetermined beam shape and predetermined distribution of energydensity.

[0058] The distribution of the energy density in this laser beam iscorrected by two homogenizers 604 and 605.

[0059] The homogenizer 604 has a function of correcting the energydensity of the laser beam which is ultimately shaped into a linearconfiguration in the direction of the width of the same. However, sincethe dimension of the linear laser beam in the direction of its width ison the order of a few millimeters, the effect of the homogenizer 604 isnot so significant.

[0060] The homogenizer 605 has a function of correcting the energydensity of the laser beam which is ultimately shaped into a linearconfiguration in the longitudinal direction of the same. Since the laserbeam extends 10 cm or more, the optical parameters of this homogenizer605 must be carefully set.

[0061] Lenses 606, 607 and 609 have a function of shaping a laser beaminto a linear configuration. 608 designates a mirror.

[0062] The configuration shown in FIGS. 6(A) and 6(B) is characterizedin that only the homogenizer 605 has major parameters that decidewhether or not variation occurs in the radiation energy density of alinearly shaped laser beam in the longitudinal direction thereof.Therefore, the configuration is characterized in that it is easy to setoptical parameters for preventing the occurrence of variation inannealing in the longitudinal direction of a linear laser.

[0063] In the configuration shown in this embodiment, the homogenizer605 is formed by twelve cylindrical lenses (having a width of 5 mm) anda laser beam incident thereupon is split into ten beams.

[0064] Specifically, the homogenizer is provided with some redundancyrelative to a laser beam such that the ten inner cylindrical lenses aremainly used. The width of the homogenizer is larger than the width ofthe laser beam incident upon the homogenizer.

[0065] In the present embodiment, the length of the ultimately radiatedlinear laser beam is 12 cm in its longitudinal direction.

[0066] The use of the configuration shown in this embodiment makes itpossible to correct variation in the energy density of a linear laserbeam in the longitudinal direction thereof and to perform homogeneousannealing on a semiconductor material.

[0067] A second embodiment of the present invention will now bedescribed.

[0068] The present embodiment shows an example of fabrication of a thinfilm transistor utilizing the present invention. FIGS. 4(A) though 4(F)illustrate steps of fabricating a thin film transistor.

[0069] First, a silicon oxide film or silicon nitride film 402 as abacking layer is formed to a thickness of 3000 Å on a glass substrateindicated by 401 using a sputtering process or plasma CVD process.

[0070] Next, an amorphous silicon film 403 is formed to a thickness of500 Å using a plasma CVD process or low pressure thermal CVD process.The use of a low pressure thermal CVD process is preferred as a meansfor forming the amorphous film 403 from the viewpoint of fineness of thefilm and crystallinity of a crystalline silicon film produced latertherefrom.

[0071] In order to improve the effect of annealing using irradiationwith a laser beam, it is important that the thickness of the amorphousfilm 403 is 1000 Å or less and more preferably 500 Å or less. The lowerlimit for the thickness of the amorphous film 403 is about 200 Å.

[0072] Next, a metal element for promoting crystallization of silicon isintroduced. Ni is used here as the metal element for promotingcrystallization of silicon. Instead of Ni, it is possible to use Fe, Co,Cu, Pd, Pt, Au, etc.

[0073] Here, Ni is introduced using a nickel acetate solution.Specifically, a nickel acetate solution prepared to have a predeterminedconcentration of Ni (10 ppm by weight here) is first dropped on thesurface of the amorphous silicon film 403. Thus, an aqueous film 404made of the nickel acetate solution is formed (FIG. 4(A)).

[0074] Next, spin drying is performed using a spin coater (not shown) toblow out any excess solution. Further, a heating process is performedfor four hours at 550° C. to obtain a crystalline silicon film 405 (FIG.4(B)).

[0075] When the crystalline silicon film 405 is obtained, it isirradiated with a laser beam. The irradiation with a laser beam improvesthe crystallinity. Here, laser annealing is carried out by irradiatingwith a KrF excimer laser whose beam is processed into a linear shapewhile scanning the laser.

[0076]FIG. 5 shows this laser annealing process. The laser beam isshaped into a linear configuration as indicated by 502 using the opticalsystem as shown in FIGS. 1(A) and 1(B).

[0077] By moving the substrate in the direction of the arrow in FIG. 5during irradiation, the linear laser beam is radiated such that it isscanned in the direction perpendicular to the longitudinal direction ofthe linear configuration.

[0078] In FIG. 5, 501 designates a region which has not been irradiatedwith the laser beam yet while 503 designates a region which has alreadybeen irradiated with the laser beam.

[0079] Here, the optical parameters of a homogenizer as shown in FIG. 2are set such that the width thereof indicated by “a” becomes 5 mm orless (the lower limit is preferably about 0.1 mm) and such that itsplits a laser beam incident thereupon into ten or more beams.

[0080] This makes it possible to correct variation in the radiationenergy density of the linear laser beam 502 in the longitudinaldirection thereof and to homogenize the effect of annealing in the samedirection.

[0081]FIG. 9 shows an example of a profile of a rectangular wave laserbeam which is split by the homogenizer into nine beams. The profile ofthe rectangular wave laser beam corresponds to a beam profile of alinear laser in the direction of the width thereof.

[0082]FIG. 10 shows an example of a profile of a rectangular wave laserbeam which is split by the homogenizer into eighteen beams. As apparentfrom comparison between FIGS. 9 and 10, the homogeneity of a laser beamcan be improved by splitting it into an increased number of beams.

[0083] The higher energy density in FIG. 10 is regarded attributable toa difference in loss between the different optical systems.

[0084] Laser annealing as shown in FIG. 4(C) is performed to obtain acrystalline silicon film 406 having higher crystallinity.

[0085] Patterning is then performed to form a region 406 which is toserve as an active layer of a thin film transistor (FIG. 4(D)).

[0086] Further, a silicon oxide film 407 is formed which covers theactive layer 406 to serve as a gate insulation film. Here, a siliconoxide film having a thickness of 1000 Å is formed using a plasma CVDprocess as the gate insulation film 407.

[0087] Next, an aluminum film (not shown) having a thickness of 5000 Åis formed which is to serve as a gate electrode. The aluminum filmincludes 0.1% scandium by weight for preventing the occurrence ofhillocks and whiskers during subsequent steps.

[0088] Hillocks and whiskers are protrusions in the form of needles orthorns formed as a result of abnormal growth of aluminum.

[0089] A resist mask (not shown) is then provided to pattern an aluminumfilm (not shown). Thus, a pattern is formed which is to constitute agate electrode 408. When the pattern to constitute the gate electrode408 is formed, an anodic oxide film is formed with the above-describedresist mask left in place.

[0090] Here, an aqueous solution including 3% nitric acid is used as theelectrolyte. Specifically, a current is applied between the aluminumfilm pattern (not shown) serving as an anode and platinum serving as acathode in this aqueous solution to form an anodic oxide film on anexposed surface of the aluminum film pattern.

[0091] The anodic oxide film 409 formed in this step is porous. Further,the porous anodic oxide film is formed on lateral sides of the patternas indicated by 409 because of the presence of the resist mask (notshown).

[0092] The thickness of the porous anodic oxide film 409 is 3000 Å. Anoffset gate region can be formed with the same thickness as this porousanodic oxide film 409.

[0093] Next, the resist mask (not shown) is removed, and anodization isperformed again. The electrolyte used in this step is an ethylene glycolsolution including 3% tartaric acid neutralized by ammonia.

[0094] An anodic oxide film 410 formed in this step has fine filmquality. In this step, the fine anodic oxide film 410 having a thicknessof 500 Å is formed through adjustment of the applied voltage.

[0095] Since the electrolyte enters the porous anodic oxide film 409,the anodic oxide film having fine film quality is formed in contact withthe gate electrode 408 as indicated by 410.

[0096] If this anodic oxide film having fine film quality is made thick,an offset gate region having the same thickness can be formed later. Inthis case, however, such a contribution to the formation of an offsetgate region is ignored because the thickness is small.

[0097] Thus, the state as shown in FIG. 4(D) is achieved. When the stateas shown in FIG. 4(D) is achieved, ion implantation is carried out toform source and drain regions. P (phosphorus) ions are implanted here tofabricate an N-channel type thin film transistor.

[0098] When the implantation of impurity ions is performed in the stateas shown in FIG. 4(D), the impurity ions are implanted in regionsindicated by 411 and 415. Regions 412 and 414 are regions in which noimpurity ion is implanted and which are not subjected to a field effectof the gate electrode 408. The regions 412 and 414 serve as offset gateregions.

[0099] The region indicated by 413 serves as a channel formation region.Thus, the state as shown in FIG. 4(E) is achieved.

[0100] When the above-described implantation of impurity ions isfinished, a laser beam is radiated to activate the regions in which theimpurity ions have been implanted. The radiation of a laser beam is alsoperformed using a laser radiation apparatus having the optical system asshown in FIGS. 1(A) and 1(B) and an irradiation method as shown in FIG.5.

[0101] When the state as shown in FIG. 4(E) is achieved, a layerinsulation film 416 is formed of a silicon oxide film, silicon nitridefilm, silicon oxynitride film, or a laminated film consisting of them.

[0102] Contact holes are then formed to form a source electrode 417 anda drain electrode 418. Thus, a thin film transistor as shown in FIG.4(F) is completed.

[0103] A third embodiment of the present invention will now bedescribed.

[0104] The present embodiment is an example wherein an XeCl laser(having a wavelength of 308 nm) is used in the configuration asdescribed in the second embodiment.

[0105] The use of a KrF excimer laser having a short wavelength (248 nm)is preferred from the viewpoint of the annealing effect on the siliconfilm. This is because a laser beam having a shorter wavelength is moreeasily absorbed by the silicon film.

[0106] However, when the maintenance of the apparatus and the stabilityof the oscillator is taken into consideration, it is preferable to usean XeCl excimer laser having a wavelength longer than that of a KrFexcimer laser.

[0107] The reason is that a longer wavelength means lower photon energy(hν) and a lighter load to the optical system and oscillator.

[0108] A fourth embodiment of the present invention will now bedescribed.

[0109] What is implied by FIG. 7 is that it is preferable in view of thehomogeneity of irradiation density that the length of a laser beam onthe final irradiation plane, as corresponding to one of cylindricallenses constructing a homogenizer, is set to about 5 mm to 15 mm.

[0110] In other words, it is preferable that the quotient, as calculatedby dividing the longitudinal length of the linear laser beam on theirradiation plane by the number of cylindrical lenses, be about 5 mm to15 mm.

[0111] If the aforementioned condition is satisfied, the length of thelinear laser beam on the irradiation plane may be 700 mm or more.

[0112] The present embodiment should not be limited to the condition, asspecified in FIG. 7, but relates to an example, in which the upper limitof the longitudinal length of the linear laser beam on the irradiationplane is not restricted, as shown in FIG. 11.

[0113] In this example, the combination of the length x of the linearlaser beam on the irradiation plane and the number y of the cylindricallenses can be selected to satisfy the formula:

(43/600)x-(1/6)≦y≦(x/5).

[0114] Here, the length x is preferably selected from the range of x≧7,more preferably x≧10.

[0115] If the length of the linear laser beam on the irradiation planeis 1000 mm, for example, the number of cylindrical lenses may beselected from the range of 72 to 200.

[0116] If there is utilized a homogenizer having one hundred cylindricallenses, on the contrary, the length of the linear laser beam on theirradiation plane may be selected from the range of 500 to 1,398 mm. Inother words, the optical system may be so designed that the length ofthe linear laser beam on the irradiation plane be confined within therange of 500 mm to 1,398 mm.

[0117] Incidentally, it is important that the width of the cylindricallens be selected from the range of 0.1 mm to 5 mm, when the combinationof the length of the linear laser beam on the irradiation plane and thenumber of cylindrical lenses is selected from the range of theaforementioned formula.

[0118] The use of the present invention makes it possible to provide atechnique which allows homogeneous annealing on a larger area during alaser process utilized in fabrication of a semiconductor device.

[0119] Although preferred embodiments of the present invention have beenillustrated and described, various alternatives, modifications andequivalents may be used. Therefore, the foregoing description should notbe taken as limiting the scope of the invention which is defined by theappended claims.

What is claimed is:
 1. A method for forming a semiconductor devicecomprising: forming a semiconductor film comprising silicon to become atleast a channel formation region over a substrate; irradiating a linearlaser light to said semiconductor film; homogenizing energy density ofsaid linear laser light in the longitudinal direction thereof by ahomogenizer; and forming a gate electrode adjacent to said semiconductorfilm with a gate insulating film therebetween, wherein length of saidlinear laser light in the longitudinal direction thereof, as anabscissa, and the number of cylindrical lenses of said homogenizer, asan ordinate, are set in the range defined by coordinates represented by(100, 7), (700, 50), (700, 140), and (100, 20) where said length of saidlinear laser light is measured in millimeters.
 2. A method for forming asemiconductor device comprising: forming a semiconductor film comprisingsilicon to become at least a channel formation region over a substrate;irradiating a linear laser light to said semiconductor film;homogenizing energy density of said linear laser light in thelongitudinal direction thereof by a homogenizer; and forming a gateelectrode adjacent to said semiconductor film with a gate insulatingfilm therebetween, wherein width of a cylindrical lense of saidhomogenizer is in the range from 0.1 mm to 5 mm.
 3. A method for forminga semiconductor device comprising: forming a semiconductor filmcomprising silicon to become at least a channel formation region over asubstrate; homogenizing energy density of a laser light, in a widthdirection thereof, incident upon a homogenizer; shaping said laser lightinto a linear laser light; irradiating said linear laser light to saidsemiconductor film; and forming a gate electrode adjacent to saidsemiconductor film with a gate insulating film therebetween, whereinsaid width direction corresponds to a longitudinal direction of saidlinear laser light, and wherein width (mm) of said laser light, in saidwidth direction, incident upon said homogenizer, as an abscissa, andwidth (mm) of a cylindrical lens of said homogenizer, as an ordinate,are set in the range defined by coordinates represented by (30, 0.1),(80, 0.1), (80, 5), (50, 5) and (30, 3).
 4. A method for forming asemiconductor device comprising: forming a semiconductor film comprisingsilicon to become at least a channel formation region over a substrate;irradiating a linear laser light to said semiconductor film;homogenizing energy density of said linear laser light in thelongitudinal direction thereof by a homogenizer; and forming a gateelectrode adjacent to said semiconductor film with a gate insulatingfilm therebetween, wherein the number y of cylindrical lenses of saidhomogenizer and length x (mm) of said linear laser light on saidsemiconductor film satisfy a formula: (43/600)x−(1/6)≦y≦(x/5).
 5. Amethod according to claim 1 wherein said laser light is selected fromthe group consisting of a KrF excimer laser light and a XeCl excimerlaser light.
 6. A method according to 3 wherein width of saidhomogenizer is larger than said width of said laser light, in said widthdirection, incident upon said homogenizer.
 7. A method according toclaim 1 wherein said semiconductor film has a thickness of 1000 Å orless.
 8. A method according to claim 1 further comprising the step ofcrystallizing said semiconductor film by heat treatment to form thecrystallized semiconductor film wherein crystallinity of saidcrystallized semiconductor film is improved by the irradiation of saidlinear laser light.
 9. A method according to claim 1 further comprisingthe step of crystallizing said semiconductor film by heat treatment toform the crystallized semiconductor film wherein said crystallizedsemiconductor film is annealed by the irradiation of said linear laserlight.
 10. A method according to claim 2 wherein said laser light isselected from the group consisting of a KrF excimer laser light and aXeCl excimer laser light.
 11. A method according to claim 2 wherein saidsemiconductor film has a thickness of 1000 Å or less.
 12. A methodaccording to claim 2 further comprising the step of crystallizing saidsemiconductor film by heat treatment to form the crystallizedsemiconductor film wherein crystallinity of said crystallizedsemiconductor film is improved by the irradiation of said linear laserlight.
 13. A method according to claim 2 further comprising the step ofcrystallizing said semiconductor film by heat treatment to form thecrystallized semiconductor film wherein said crystallized semiconductorfilm is annealed by the irradiation of said linear laser light.
 14. Amethod according to claim 3 wherein said laser light is selected fromthe group consisting of a KrF excimer laser light and a XeCl excimerlaser light.
 15. A method according to claim 3 wherein saidsemiconductor film has a thickness of 1000 Å or less.
 16. A methodaccording to claim 3 further comprising the step of crystallizing saidsemiconductor film by heat treatment to form the crystallizedsemiconductor film wherein crystallinity of said crystallizedsemiconductor film is improved by the irradiation of said linear laserlight.
 17. A method according to claim 3 further comprising the step ofcrystallizing said semiconductor film by heat treatment to form thecrystallized semiconductor film wherein said crystallized semiconductorfilm is annealed by the irradiation of said linear laser light.
 18. Amethod according to claim 4 wherein said laser light is selected fromthe group consisting of a KrF excimer laser light and a XeCl excimerlaser light.
 19. A method according to claim 4 wherein saidsemiconductor film has a thickness of 1000 Å or less.
 20. A methodaccording to claim 4 further comprising the step of crystallizing saidsemiconductor film by heat treatment to form the crystallizedsemiconductor film wherein crystallinity of said crystallizedsemiconductor film is improved by the irradiation of said linear laserlight.
 21. A method according to claim 4 further comprising the step ofcrystallizing said semiconductor film by heat treatment to form thecrystallized semiconductor film wherein said crystallized semiconductorfilm is annealed by the irradiation of said linear laser light.